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PubMed1996

Cardiovascular effects of exercise: role of endothelial shear stress.

Experimental, epidemiologic and clinical studies have provided strong evidence that physical exercise has beneficial effects on multiple physiological variables affecting cardiovascular health (lipoprotein levels, rest blood pressure and heart rate, carbohydrate tolerance, neurohormonal activity). Regular exercise has been shown to slow the progression of cardiovascular disease and to reduce cardiovascular morbidity and mortality. More recently, exercise-induced increases in blood flow and shear stress have been observed to enhance vascular function and structure. By increasing the release of nitric oxide and prostacyclin, shear stress augments endothelium-dependent vasodilation and inhibits multiple processes involved in atherogenesis and restenosis. In this review we discuss the underlying mechanisms by which exercise-induced blood flow and shear stress exert their salutary effects on cardiovascular remodeling.

Arteriosclerosis↗

PubMed1987

A data acquisition system for clinical research.

We developed a system for automatic collection and synchronization of multiple physiological variables during clinical investigations. Centered around an eight-track instrumentation tape recorder, the system solves several problems encountered in gathering this type of research data: (1) slowly changing variables are digitized and compressed onto a single track by recording them in one serial message, allowing for recording many more variables than there are tape tracks available; (2) simultaneous analog recording allows retention of original data for variables that may be processed subsequently by multiple schemes; (3) data acquisition is verified with both analog chart recording and numerical video display monitors; (4) off-line computer processing time is decreased at least twofold by using tape playback speeds faster than the recording speed; (5) cost is kept low by using an inexpensive 1/4-inch (0.64-cm) tape medium and dedicated microcomputers; and (6) the system is unobtrusive, portable, and easily reconfigured for different clinical studies. It proved to be reliable in a study of more than 80 patients undergoing cardiac surgery.

Computers↗

PubMed2000

Abdominal perfusion pressure: a superior parameter in the assessment of intra-abdominal hypertension.

OBJECTIVE: To assess the clinical utility of abdominal perfusion pressure (mean arterial pressure minus intra-abdominal pressure) as both a resuscitative endpoint and predictor of survival in patients with intra-abdominal hypertension. METHODS: 144 surgical patients treated for intra-abdominal hypertension between May 1997 and June 1999 were retrospectively reviewed. Multivariate logistic regression and receiver operating characteristic curve analysis of common physiologic variables and resuscitation endpoints were performed to determine the decision thresholds for each variable that predict patient survival. RESULTS: Abdominal perfusion pressure was statistically superior to both mean arterial pressure and intravesicular pressure in predicting patient survival from intra-abdominal hypertension and abdominal compartment syndrome. Multiple regression analysis demonstrated that abdominal perfusion pressure was also superior to other common resuscitation endpoints, including arterial pH, base deficit, arterial lactate, and hourly urinary output. CONCLUSION: Abdominal perfusion pressure appears to be a clinically useful resuscitation endpoint and predictor of patient survival during treatment for intra-abdominal hypertension and abdominal compartment syndrome.

Abdominal Injuries↗

PubMed1996

Cerebroprotective effects of aminoguanidine in a rodent model of stroke.

BACKGROUND AND PURPOSE: During a cerebral infarction, a complex cascade of cytotoxic events ultimately determines the volume of brain cell loss. The studies presented here demonstrate that aminoguanidine, an experimental therapeutic currently in clinical trials to prevent diabetic complications, is cerebroprotective in focal cerebral infarction. METHODS: Adult Lewis rats (n = 6 to 12 per group) were anesthetized with ketamine and subjected to focal cerebral infarction by tandem permanent occlusion of the right middle cerebral artery and ipsilateral common carotid artery (CCA), followed by temporary occlusion of the contralateral CCA. Infarct volume (cortical) was assessed 24 hours after the onset of ischemia by planimetric analysis of coronal brain slices stained with tetrazolium. RESULTS: Aminoguanidine (320 mg/kg IP) administered 15 minutes after the onset of ischemia resulted in a significant reduction of infarct volume (7.6 +/- 2.6% of hemisphere in controls versus 1.3 +/- 0.2% of hemisphere in aminoguanidine-treated rats; P < .05). Administration of aminoguanidine conferred significant cerebroprotection even when administered 1 or 2 hours after the onset of ischemia (88% and 85% reduction from control, respectively; P < .05). Cerebroprotection by aminoguanidine was independent of systemic physiological variables known to influence stroke size (eg, temperature, mean arterial blood pressure, blood glucose, and arterial pH, PCO2, and PO2). CONCLUSIONS: These results indicate that the stroke-reducing properties of aminoguanidine are dose and time dependent, with substantial cerebroprotection persisting even with drug delivery up to 2 hours after the onset of ischemia. It is now plausible to pursue development of aminoguanidine as an experimental therapeutic in stroke, and possible mechanisms of these cerebroprotective effects are under consideration.

Animals↗

PubMed1988

The evaluation of quantitative autoradiogram processing systems for cerebrovascular research.

The development of an image processing system for quantitative autoradiography (QAR) is described, with emphasis on the evaluation of image digitization systems independent of hardware or software design. Each step of converting the autoradiographic image to a functional image of a physiological variable such as local cerebral blood flow (LCBF) or local cerebral glucose utilization rate (LCGU) is evaluated. The autoradiograms are digitized, aligned, transformed to a tissue tracer concentrations image based on the gray value (GV) of calibrated 14C standards, subtracted from each other as required in double tracer QAR, and converted to an LCBF or LCGU image using the proper tracer kinetic model. Geometric size, mean and standard deviation of the LCBF, LCGU, and tracer concentration can be measured in regions of interest. These steps are evaluated separately for their contribution to the accuracy and precision of the final, functional image. The qualities important in the final image are spatial resolution, intensity linearity, and intensity sensitivity, as well as the noise level. Techniques for evaluating the LCBF image include: (1) optimization of the input linearity and dynamic range of the video camera to maximize relative intensity sensitivity of the final functional image; (2) visual inspection of the curves used to fit various functions that are important in the conversion of the GV image to an image of physiological interest; (3) consideration of the noise introduced by the input devices and during the image conversion; and (4) above all, the integration of the various parts of the system to produce an accurate image useful in cerebrovascular research.

Autoradiography↗

PubMed1998

Hormonal influences on stress-induced neutrophil mobilization in health and chronic fatigue syndrome.

This investigation tested the hypotheses that women diagnosed with chronic fatigue syndrome (CFS) would exhibit significantly greater systemic indices of exercise-induced leukocyte mobilization and inflammation (neutrophilia, lactoferrin release, complement activation) than controls matched for age, weight, and habitual activity and that responses in the luteal phase of the menstrual cycle would be greater than in the follicular phase. Subjects stepped up and down on a platform adjusted to the height of the patella for 15 min, paced by metronome. Blood samples were collected under basal conditions (the day before exercise) and following exercise for determination of circulating neutrophils and plasma concentrations of lactoferrin, C3a des arg, and creatine kinase. Complete, 24-hr urine collections were made for determination of cortisol excretion. For all subjects, circulating neutrophil counts increased 33% (P < 0.0001) and lactoferrin increased 27% (P = 0.0006) after exercise, whereas plasma C3a des arg and creatine kinase did not increase. No indication of an exaggerated or excessive response was observed in the CFS patients compared to the controls. In healthy women, circulating neutrophil numbers exhibited previously described relationships with physiological variables: basal neutrophil counts correlated with plasma progesterone concentrations (R = 0.726, P = 0.003) and the exercise-induced neutrophilia correlated with both urinary cortisol (R = 0.660, P = 0.007) and plasma creatine kinase (R = 0.523, P = 0.038) concentrations. These relationships were not observed in the CFS patients (R = 0.240, P = 0.370; R = 0.042, P = 0.892; and R = 0.293, P = 0.270; respectively). These results suggest that normal endocrine influences on the circulating neutrophil pool may be disrupted in patients with CFS.

Cell Count↗

PubMed2001

Functional community ambulation requirements in incomplete spinal cord injured subjects.

STUDY DESIGN: A group of people with incomplete spinal cord injuries (SCI) were evaluated and compared with able-bodied individuals during several walking conditions. OBJECTIVES: To evaluate the functional community ambulation and estimated energy expenditure in persons with incomplete SCI and able-bodied individuals. METHODS: A list of criteria was used to evaluate functional community ambulation among participants. Physiological variables, such as the heart rate, oxygen uptake and the lactate concentration, were also measured. RESULTS: Three of nine incomplete SCI subjects and all able-bodied subjects were able to meet all the criteria measured. The required velocity to safely cross an intersection was the criterion that the incomplete SCI group had the most difficulty reaching. The able-bodied subjects had a comfortable walking velocity twice that of the incomplete SCI subjects' preferred velocity. When walking at the same velocity (incomplete SCI subjects' preferred velocity), the incomplete SCI subjects had a rate of oxygen uptake 26% greater than the healthy subjects and were 200% less efficient. The lactate concentration also proved to be a useful tool when evaluating the incomplete SCI subjects' walking efficiency. The incomplete SCI subjects lactate concentration increased after walking at their preferred velocity, meaning that the anaerobic pathways were used to meet energy demands. CONCLUSION: Rehabilitation centers should adapt their evaluation forms and increase their criteria requirements to more suitable criteria that are found in the SCI patient's community. The physiological cost should also be taken into consideration when evaluating the SCI patient's functional ambulation.

Activities of Daily Living↗

PubMed2001

Continuous measurement of breathlessness during exercise: validity, reliability, and responsiveness.

A continuous method for recording changes in breathlessness (dyspnea) during exercise is introduced and compared with the traditional discrete method. In study 1, a category-rating scale was presented on a computer screen, and 14 healthy, young female subjects exercised on a cycle ergometer until exhaustion. Two approaches were used to obtain ratings of breathlessness: a discrete method, in which subjects gave single judgments every minute, and a continuous method, in which subjects throughout exercise moved the mouse so that a bar on the screen extended to the desired location along the scale. Psychophysical results relating measures of breathlessness and the variables of work, oxygen consumption, and minute ventilation were statistically indistinguishable with the two methods, and both methods were highly reliable across test sessions. In study 2, both measurement methods were employed, and the subjects were 14 healthy, young males. In each of two sessions (discrete or continuous method), subjects first rated their breathlessness during an incremental test in which the workload was increased over time and levels of work, and minute ventilation were recorded. Subjects then exercised for 10 min at 60% of the maximal oxygen consumption achieved during the incremental test. At two points during steady-state exercise, a respiratory load was introduced that lasted for 1 min. It was possible to determine the responsiveness of subjects to onset and offset of the respiratory load for the continuous method but not for the discrete method. In study 3, patients with chronic obstructive pulmonary disease employed both methods, and it was found that the continuous method was better at determining whether subjects showed a significant positive slope of the regression line between breathlessness ratings and physiological variables.

Adult↗

PubMed1991

Analysis of morbidity and mortality rates in right hepatectomy with the preoperative APACHE II score.

Morbidity and mortality rates in 70 patients who underwent major liver resection for liver tumors (primary and metastatic) were determined and correlated with the preoperative APACHE II score. Patients were divided into three groups according to their preoperative APACHE II score: low (0 to 3), mid (4 to 7), and high (8 and above). A higher score was closely correlated with increased postoperative morbidity and operative mortality rates. The group with low scores had a postoperative morbidity rate of 34% and a mortality rate of 0%, the group with mid scores had a postoperative morbidity rate of 54% and a mortality rate of 3%, and the group with high scores had a postoperative morbidity rate of 80% and a mortality rate of 20%. Age did not correlate with morbidity. It was therefore postulated that morbidity and mortality rates were related to the combination of points for abnormal physiologic variables and points for chronic health, or APACHE II score minus points for age. As the combination of these points increases the postoperative morbidity and operative mortality rates increase significantly (from 24% in the 0-point group to 69% in the greater than or equal to 3-point group). Also the two deaths occurred in the group with 3 or more points. The preoperative APACHE II score may be used by clinicians to evaluate before surgery the risk of postoperative morbidity and death in elective major liver surgery.

Adult↗

PubMed1990

Secondary insults during intrahospital transport of head-injured patients.

Secondary pathophysiological insults occurring after injury have been prospectively assessed in 50 head-injured patients who required intrahospital transfer. 35 patients were transported from the intensive care unit (ICU) and 15 from the accident and emergency department. Physiological variables were recorded every minute in the four hours before transfer (ICU group only), during the move, and for four hours afterwards. Pretransfer insults were predictive of further insults during and after transport. There was significant correlation between increased frequency of insults post-transfer (compared with pre-transfer) and high injury severity score. A greater proportion of the patients transported from the emergency department had secondary injuries post-transfer. Adequate resuscitation before moving the patient, especially in patients with multiple injury, is important.

Adolescent↗

PubMed1989

Arterio-venous concentration difference of [51Cr]EDTA after a single injection in man. Significance of renal function and local blood flow.

The present investigation was undertaken in order to study (1) the difference in arterial (Ca) and venous (Cv) concentration of [51Cr]EDTA (ethylenediaminetetraacetate) after a single intravenous injection, (2) the impact of different physiological variables on this difference, and (3) the error introduced in the measurement of renal plasma clearance and total plasma clearance by using venous blood samples instead of arterial. In 13 patients with GFR ranging from 29 to 150 ml min-1, Ca was higher than Cv immediately after the injection. After mean 38 min (range 12-82 min) the two curves crossed, and 180-300 min post-injection (p.i.) Cv was 5.9% higher than Ca (range 0.5-13.9%, P less than 0.001). The more reduced renal function, the smaller was the concentration difference. The areas under the arterial and the venous plasma concentration curves did not differ significantly at either 0-infinity or 0-300 min p.i. whereas the venous area 0-100 min p.i. underestimated the arterial area in the same period by 4.1% (P less than 0.05). In a computer simulation model, variation in the forearm capillary permeability-surface area product did not have any significant influence on the Cv-Ca difference, whereas the difference was very sensitive to even small changes in forearm blood flow within the physiological range. For measurement of renal plasma clearance it is recommended to use one long period: from the time of injection until 300 min p.i. or longer. If the clearance period is too short, the use of venous samples will overestimate the true renal clearance. Plasma clearance determined by venous and arterial blood samples does not differ significantly as long as the concentration is followed from the time of injection and a long period is applied. When simplified plasma clearance techniques are used, different results may be obtained from venous and arterial samples. The simplified techniques using venous blood samples--which usually include some empirical corrections--should be sufficiently reliable in daily clinical practice provided the forearm blood flow is reasonably high, e.g. exposure to cold should be avoided.

Adult↗

PubMed2004

Carbon dioxide monitoring and evidence-based practice - now you see it, now you don't.

Carbon dioxide has been monitored in the body using a variety of technologies with a multitude of applications. The monitoring of this common physiologic variable in medicine is an illustrative example of the different levels of evidence that are required before any new health technology should establish itself in clinical practice. End-tidal capnography and sublingual capnometry are two examples of carbon dioxide monitoring that require very different levels of evidence before being disseminated widely. The former deserves its status as a basic standard based on observational data. The latter should be considered investigational until prospective controlled data supporting its use become available. Other applications of carbon dioxide monitoring are also discussed.

Anesthesia, Endotracheal↗

PubMed1990

Physiological features of edematous dogs unresponsive to atrial natriuretic peptide.

Sodium-retaining cirrhotic and chronic caval dogs with ascites show a heterogeneous natriuretic response to atrial natriuretic factor (ANF) infusions such that half will increase their urinary excretion of sodium and half will show no natriuretic response whatsoever. In these studies we have examined several physiological variables that might discriminate between these two experimental populations. We studied 22 caval dogs (11 natriuretic responders, 11 nonresponders) and 19 cirrhotic dogs (9 responders, 10 nonresponders). After an infusion of rat ANP-(1-28), 125 ng.kg-1.min-1, differences in glomerular filtration rate, blood pressure, or urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP) could not differentiate between the two types of dogs. When the left kidney of nonresponding dogs in both the caval and cirrhotic groups was either denervated or vasodilated with acetylcholine bromide (60-80 micrograms/min), the attenuation of the natriuretic response to ANF was not reversed. Papillary plasma flow (PPF) after ANF infusion was measured by a Lillienfield technique and averaged 36 +/- 4 ml.min-1.100 g-1 in normal dogs, 10.7 +/- 0.7 ml.min-1.100 g-1 in both responding and nonresponding caval dogs, and 48.3 +/- 1.1 ml.min-1.100 g-1 for each group of cirrhotic dogs. We conclude that differences in renal perfusion, PPF, cGMP generation, or the presence of intact renal nerves cannot explain the lack of a post-ANF natriuretic response in half of caval or cirrhotic dogs. Other physiological determinants must explain the heterogeneity of natriuretic response to ANF observed in edematous dogs.

Animals↗

PubMed2002

Subjective sleep quality in cystic fibrosis.

OBJECTIVES: To evaluate sleep quality in patients with cystic fibrosis (CF). METHODS: The Pittsburgh Sleep Quality Index (PSQI) questionnaire was administered to 37 CF patients with moderate to severe lung disease in a clinically stable state. Sleep studies were performed concurrently. PSQI scores were correlated with results of anthropometric variables, arterial blood gas tensions, lung function variables, and polysomnographic variables. Potential differences in objective measurements between patients with high and low scores on the PSQI were assessed. RESULTS: Thirty-seven patients with CF were studied, aged 27+/-8 (mean+/-1 SD) years and forced expiratory volume in 1 s (FEV(1)) 36+/-12% predicted. The mean PSQI was 5.7+/-4.0. Fourteen of the 37 patients had a high PSQI, i.e. >5. Significant correlations between objective variables and both component scores and total PSQI were as follows: age and 'subjective sleep quality' (r=0.4, P<0.05), age and 'sleep duration' (r=0.3, P<0.05), FEV(1) % predicted and 'subjective sleep quality' (r=-0.4, P<0.05), carbon monoxide transferred per litre of lung volume (KCO) % predicted and 'daytime dysfunction' (r=-0.4, P<0.01), PaCO(2) and 'sleep latency' (r=0.4, P<0.01), arterial carbon dioxide tension (PaCO(2)) and 'habitual sleep efficiency' (r=0.3, P<0.05), PaCO(2) and total PSQI (r=0.4, P<0.05), absolute minimum sleep oxyhemoglobin saturation by pulse oximetry (SpO(2) %) and 'sleep latency' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and 'sleep duration' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and total PSQI (r=-0.4, P<0.05) and awake transcutaneous CO(2) and 'sleep duration' (r=0.45, P<0.05). Better sleep efficiency (P<0.05) and a greater % of rapid eye movement (REM) sleep (P<0.05) were found in those patients with a PSQI of < or =5. CONCLUSIONS: A number of CF patients reported poor sleep quality. A relationship was shown between subjective sleep quality and physiological variables describing disease severity. Better sleep efficiency and % REM sleep were seen in patients with low PSQI scores. These results suggest a useful role for the PSQI in assessing sleep quality in patients with CF.

Journal Article↗

PubMed2006

[Monitoring in acute cerebral infarction].

BACKGROUND: Cerebral ischaemia is potentially reversible during the first few hours. Monitoring of physiological variables such as temperature, blood pressure, heart rhythm, oxygen saturation and cerebral blood flow may be important for efficient treatment and reduction of the infarct volume. MATERIAL AND METHODS: This article is based on a review of relevant articles in international journals over the last 15 years on the pathophysiology of acute ischaemic stroke and treatment in intensive stroke units compared with conventional stroke units. RESULTS AND DISCUSSION: Two pilot studies indicate that continuous monitoring in intensive stroke units improves outcome compared with conventional stroke units. Future studies must draw the balance between continuous monitoring and mobilization in the early phase of ischaemic stroke.

Acute Disease↗

PubMed2006

Gender associated differences in determinants of quality of life in patients with COPD: a case series study.

BACKGROUND: The influence of gender on the expression of COPD has received limited attention. Quality of Life (QoL) has become an important outcome in COPD patients. The aim of our study was to explore factors contributing to gender differences in Quality of Life of COPD patients. METHODS: In 146 men and women with COPD from a pulmonary clinic we measured: Saint George's Respiratory Questionnaire (SGRQ), age, smoking history, PaO2, PaCO2, FEV1, FVC, IC/TLC, FRC, body mass index (BMI), 6 minute walk distance (6MWD), dyspnea (modified MRC), degree of comorbidity (Charlson index) and exacerbations in the previous year. We explored differences between genders using Mann-Whitney U-rank test. To investigate the main determinants of QoL, a multiple lineal regression analysis was performed using backward Wald's criteria, with those variables that significantly correlated with SGRQ total scores. RESULTS: Compared with men, women had worse scores in all domains of the SGRQ (total 38 vs 26, p = 0.01, symptoms 48 vs 39, p = 0.03, activity 53 vs 37, p = 0.02, impact 28 vs 15, p = 0.01). SGRQ total scores correlated in men with: FEV1% (-0.378, p < 0.001), IC/TLC (-0.368, p = 0.002), PaO2 (-0.379, p = 0.001), PaCO2 (0.256, p = 0.05), 6MWD (-0.327, p = 0.005), exacerbations (0.366, p = 0.001), Charlson index (0.380, p = 0.001) and MMRC (0.654, p < 0.001). In women, the scores correlated only with FEV1% (-0.293, p = 0.013) PaO2 (-0.315, p = 0.007), exacerbations (0.290, p = 0.013) and MMRC (0.628, p < 0.001). Regression analysis (B, 95% CI) showed that exercise capacity (0.05, 0.02 to 0.09), dyspnea (17.6, 13.4 to 21.8), IC/TLC (-51.1, -98.9 to -3.2) and comorbidity (1.7, 0.84 to 2.53) for men and dyspnea (9.7, 7.3 to 12.4) and oxygenation (-0.3, -0.6 to -0.01) for women manifested the highest independent associations with SGRQ scores. CONCLUSION: In moderate to severe COPD patients attending a pulmonary clinic, there are gender differences in health status scores. In turn, the clinical and physiological variables independently associated with those scores differed in men and women. Attention should be paid to the determinants of QoL scores in women with COPD.

Activities of Daily Living↗

PubMed1987

Weight regulation practices in athletes: analysis of metabolic and health effects.

Athletes engage in a number of dietary and weight control practices which may influence metabolism, health, and performance. This paper reviews the literature on these factors with special emphasis on athletes who show large, frequent, and rapid fluctuations in weight (wrestlers) and athletes who maintain low weight and low percent body fat (e.g., distance runners, gymnasts, and figure skaters). A theory is presented which relates these weight patterns and the accompanying dietary habits to changes in body composition, metabolism, metabolic activity of adipose tissue, and the distribution of body fat. Changes in these physiological variables may be manifested in enhanced food efficiency (weight as a function of caloric intake) as the body seeks to protect and replenish its energy stores. This may explain the surprisingly low caloric intakes of some athletes. The health status of the athlete is a concern in this regard because there may be changes in fat distribution, risk factors for cardiovascular disease, and hormonal factors associated with reproductive functioning in both females and males. Amenorrhea in female athletes may be mediated at least in part by regional fat distribution; depletion of femoral fat depots (lactational energy reserves) may be the stimulus for cessation or disruption of menses.

Adipose Tissue↗

PubMed1984

Ultradian glucocorticoid rhythms in monkeys and rats continue during stress.

Previously we showed that rhesus monkeys have ultradian cortisol rhythms with periods of about 90 min that persist during the infusion of large amounts of adrenocorticotropin. The experiments reported here showed that rats exhibit ultradian corticosterone rhythms with a similar period (median period 61 min). However, rat ultradian corticosterone rhythms were distorted by large slow trends that had to be removed before the rhythm could be adequately assessed. The need for sophisticated trend removal suggests that physiological variables that have been described as exhibiting episodic fluctuations (e.g., human cortisol) may actually be periodic and ultradian. The ultradian glucocorticoid rhythm persisted during stress both in monkeys (median period 80 min) and rats (median period 52 min). However, the glucocorticoid stress response appeared to produce large slow trends in both monkeys and rats, indicating that environmental influences may introduce slow trends that make raw data difficult to evaluate. More importantly, the fact that ultradian glucocorticoid rhythms persist during stress provides further evidence of limits on the classical concept that glucocorticoid secretion is tightly and inseparably linked to hormonal events in the hypothalamic-pituitary unit.

Adrenal Glands↗